The invention generally relates to steering controls for catheters. In a more specific sense, the invention relates to catheters that can be steered and manipulated within interior regions of the body from a location outside the body.
Physicians make widespread use of catheters today in medical procedures to gain access into interior regions of the body. It is important that the physician can control carefully and precisely the movement of the catheter within the body, especially during procedures that ablate tissue within the heart. These procedures, called electrophysiological therapy, are becoming more widespread for treat cardiac rhythm disturbances.
During these procedures, a physician steers a catheter through a main vein or artery (which is typically the femoral artery) into the interior region of the heart that is to be treated. The physician then further manipulates a steering mechanism to place the electrode carried on the tip of the catheter into direct contact with the tissue that is to be ablated. The physician directs radio frequency energy into the electrode tip to ablate the tissue and form a lesion.
Cardiac ablation especially requires the ability to precisely bend and shape the tip end of the catheter to position the ablation electrode.
The invention provides a catheter having a distal tip section that is bendable at the selection of the user in two different directions. The distal tip section assumes different predetermined curves when bent in each direction. The degree of bending or shape of the predetermined curve can be adjusted in accordance with the invention.
The invention provides a catheter having a body that is bendable in different first and second directions in response, to external forces. The catheter includes a steering mechanism that is movable in two paths for applying different external bending forces on the body and wherein the forces can be adjusted by providing for a different length of travel paths for causing bending forces in the first and second directions.
The steering mechanism includes a first actuator that operates in response to movement of the steering mechanism in the first path. The first actuator bends the body in the first direction into a first adjustable predetermined nonlinear shape.
The steering mechanism also includes a second actuator that operates in response to movement of the steering mechanism in the second path. The second actuator bends the body in the second direction into a second adjustable predetermined nonlinear shape. The second shape is different from the first shape.
In one embodiment, the bendable body includes a flexible wire member having left and right faces. In this arrangement, the steering mechanism includes left and right steering wires. The distal ends of the steering wires are attached, respectively, to the left and right faces of the wire member.
In this embodiment, the first actuator places the left steering wire into tension to bend the wire member to the left into the first adjustable nonlinear shape. The second actuator places the right steering wire into tension to bend the wire member to the right into the second adjustable nonlinear shape. The steering wires cause asymmetric bending of the wire member by virtue of the fact that the first and second actuators cause the left and right steering wires to travel different distances.
In one embodiment, the points of attachment of the distal ends of the left and right steering wires are generally symmetrically spaced on the left and right faces of the wire member. In another arrangement, the points of attachment of the distal ends of the left and right steering wires are generally asymmetrically spaced on the left and right faces of the wire member.
In one embodiment, the steering mechanism includes a rotatable cam to the lateral edges of which the proximal ends of the left and right steering wires are adjustably attached. A lever mechanism rotates the rotatable cam to the left and to the right.
In this arrangement, the first actuator includes a first cam surface formed on the left side of the rotatable cam. The first cam surface bears against and tensions the left steering wire in response to rotation of the rotatable cam to the left.
Also in this arrangement, the second actuator includes a second cam surface formed on the right side of the rotatable cam. The second cam surface is configured differently from the first cam surface and bears against and tensions the right steering wire in response to rotation of the rotatable cam to the right.
In one embodiment, the first and second cam faces form curves having different radii. Alternatively, the cam faces may be symmetrical but asymmetric steering is accomplished by adjusting the amount of travel of the steering wires.
The steering wires are preferably attached tangentially to the lateral edges of the rotatable cam and can be adjusted so that rotation of the rotatable cam results in a multitude of selectable different left and right curve shapes. In accordance with the preferred embodiment of the invention the control wires extend through adjustable stop members threaded into threaded openings in the lateral edges of the rotatable cam. The proximal ends of the wires are fixed to terminal blocks that are engaged by the stops upon rotation of the rotatable cam to thereby selectively apply tension to the wires. Preferably the steering wires are attached to the terminal blocks by having the ends thereof being bent at an angle exceeding 90xc2x0, in fishhook fashion, and being soldered into the blocks.